Various researches have been made for effectively abstracting energy of wave motion or energy stored in head waters in the oceans and rivers. For example, Japanese Patent Kokai No. 62-248876 discloses a pumping apparatus utilizing the ocean tides. This apparatus comprises a tower body erected in the bottom of the sea and projecting from the water surface, a reservoir tank arranged at the top of the tower body, a plurality of pumping tanks arranged around the tower body, pistons vertically slidably arranged within the respective pumping tanks, floats coupled to the respective pistons via a link mechanism so as to move the pistons up and down in accordance with the tidal movement, said pumping tanks being provided with respective sea water inlet ports arranged at a height located below the sea level at high tide and provided with a sea water intake valve for introducing sea water, and exhaust pipes arranged at the top of the respective pumping tanks in order to keep the pumping tanks in communication with the reservoir tank and provided with respective check valves in order to block any reverse flow of sea water from the reservoir tank to the pumping tanks.
However, the pumping efficiency of such a proposed known pumping apparatus is very low because it operates only once for a cycle of tidal movement of sea water and it is impossible to pump up water to a height of 100 m or so, making the apparatus poorly applicable to industrial use, because it was designed without considering the ratio of the cross sectional area of the floats to that of the pistons. Additionally, the link mechanism coupling each float and piston of the apparatus is complicated and hence liable to be damaged when subjected to large energy of wave motion so that there is no way of ensuring a stable operation for the user of the apparatus for a long period of time and the fact that maintenance can also pose problems which make such an apparatus hardly feasible for practical applications.
Meanwhile, the use of petroleum as a source of energy is accompanied by serious environmental problems such as destruction of nature and air pollution, aside from the fact it is a limited natural resource. Therefore, the need of developing apparatuses and plants for effectively absorbing energy from water in the sea and rivers on an industrial basis has been increasing as they can provide means for solving these problems. While effective exploitation of natural energy of this type has been discussed by scientific researchers, no major breakthrough has been made in this technical field.
In view of the above circumstances, it is therefore an object of the present invention to provide an automatic pumping apparatus utilizing wave motion that can solve the above identified problems of conventional apparatuses, operates stably for a long period of time and hence is feasible for industrial applications.